The Research On Reservoir Macroscopic Heterogeneity Of Yan9and Yan10in Zhen250Area Of Zhenyuan Oil Field In Ordos Basin

The Ordos basin is one of the large Mesozoic continental sedimentary basins in central China, here the tectonic movement is stable and it is a typical cratonic basin. It has been nearly one hundred years since we began to search for oil and gas in Ordos basin. Production practices and basic theory studies about basin suggest that the hydrocarbon accumulation and forming rules is somehow complex, the Triassic yan’an group is a very important target layer in exploration. For the accumulation of Mesozoic reservoir, the good sandbody is fundamental and the diversity of trap is necessar, therefore, in the current studies, it is very important for us to make sure the heterogeneity of reservoirs, that means we must determine the morphology, distribution and sedimentary microfacies characteristics of Yan’an group sandbody Accurately, then we need to have a further understanding of its physical properties and reservoir characteristics.This paper takes the Yan9and Yan10reservoirs of Jura in Zhenyuan oil field250area of Ordos basin as the research object. Based on a large number of geological data and predecessors’ research results as well as core observation and description in the study area, core analysis assay data and logging data, we have studied the yan9and yan10’s sedimentary characteristics, sedimentary micro facies, sand body morphology and distribution, reservoir characteristics and the distribution of the reservoir system with the theory of sedimentology, petroleum geology and geophysics while combining the field profile, drilling and logging data and this undoubtedly makes it easier for the future exploration and deveiopment of this area.Our working area is in the southwest of Shanbei slope,and part of its structure belongs to the Qingyang nose fold belt, just like a western-leaning monocline,and there is no complete structural traps found in the oil field. Zhenyuan oil field is in the south of Tianhuan depression which located in the southern basin, and this area is administrated by the shuguang town,zhenyuan city of Gansu province.In this paper, based on the logging report, logging curve analysis, we establish the Isochronous stratigraphic framework of thin layers,define the regional marker bed and use the theory of depositional cycle to make single well stratigraphic division and the isochronal contrast of diffrerent well in study area,and with the isochronal contrast of diffrerent well,we finally get a unified isochronal stratigraphic framework of whole working area. We totally compare8profiles, of which,4are northwest and the others are northeast. We find that the layers are a little continue and the change of lay thickness is not serious(15-20m), besides,the sandbody along both sides of river are controled by lithology while the river is controled by tectonic movement.Through stratigraphic division and comparasion,we divide Yan9into Yan91,Yan92and Yan93, and divide Yan10into Yan101,Yan102,Yan103.Yan9and Yan10belong to the braided river deposition. At the time of yan9, there are channel deposit, point bat deposit, Channel lateral margin deposit and flood plain deposit. In general, the sand body of Yan9reservoir is relatively developed, but most of them are empty layers or water layers, the oil layers account for a small number. There are channel deposit, Channel lateral margin deposit and flood plain deposit in Yan10, the deposition is mainly from the northeast, and the channel deposit sand is very development, it is thick and wide. Research results show that the chickness of Yan102sand body is relatively stable,that is where the oil lays locate in.The Study on the heterogeneity to reservoirs reveals that the reservoirs here are mainly composed of compound positive rhythm and simple positive rhythm while supplemented by a few homogeneous rhythm. From the point of sedimentary microfacies,the interbeds in flood plain deposit are thickest, nd the interbeds in channel and point bat are thinnest. The reservoirs heterogeneity of Yan9and Yan10are weak,they are between the scope of homogeneous and medium heterogeneity.The research on interlayer heterogeneity indicates that the main and non-main layer reservoirs’physical parameters vary greatly and the interzonal isolations are all development, the stratification coefficient and sandstone density of yan91and yan92are higher, and the same is to Yan102, the three small sand bed are development, but they are not well beddediation and onrush coefficient relative to several other small, their coefficie, coefficient of of variation and dash coefficient is smaller than the other’s. The interlayer heterogeneity of Yan9and Yan10are both strong, but the Yan10’s is stronger.When we refer to the areal heterogeneity in this working area,it means the sand’s geometric shape, the sand’s continuity in every directions, the sand’s communication,and the porosity and its permeability’s plane change and direction. The plane heterogeneity is affected by sedimentary microfacies, From point bat to the channel deposit, the Channel lateral margin, the flood plain deposits, hete rogeneity is gradually enhanced. The Statistics on porosity and permeability of Yan9and Yan10show that they are both Low porosity and medium permeability reservoirs.